This invention relates to compounds that inhibit the activity of protein kinases. Protein kinases are enzymes that catalyze the transfer of a phosphate group from ATP to an amino acid residue, such as tyrosine, serine, threonine, or histidine on a protein. Regulation of these protein kinases is essential for the control of a wide variety of cellular events including proliferation and migration. Specific protein kinases have been implicated in diverse conditions including cancer [Blume-Jensen, P., Nature, 411, 355 (2001)) Traxler, P. M., Exp. Opin. Ther. Patents, 8,1599 (1998); Bridges, A. J., Emerging Drugs, 3, 279 (1998)]; restenosis [Mattsson, E., Trends Cardiovascular Medicine 5, 200 (1995)]; atherosclerosis [Raines, E. W., Bioessays, 18, 271 (1996)]; angiogenesis [Shawver, L. K., Drug Discovery Today, 2, 50 (1997); Folkman, J., Nature Medicine, 1, 27 (1995)] stroke [Paul, R., Nature Medicine 7, 222 (2001)]; and osteoporosis [Boyce, J. Clin. Invest., 90, 1622 (1992)].
Tyrosine kinases (TK) are a class of protein kinases. The major family of cytoplasmic protein TKs is the Src family which consists of at least eight members (Src, Fyn, Lyn, Yes, Lck, Fgr, Hck and Blk) that participate in a variety of signaling pathways [Schwartzberg, P. L., Oncogene, 17, 1463 (1998)]. The prototypical member of this tyrosine kinase family is Src, which is involved in proliferation and migration responses in many cell types [Sawyer, T., Expert Opin. Investig. Drugs, 10, 1327 (2001)]. Src activity has been shown to be elevated in breast, colon (˜90%), pancreatic (>90%) and liver (>90%) tumors. Greatly increased Src activity is also associated with metastasis (>90%) and poor prognosis. Antisense Src message impedes growth of colon tumor cells in nude mice [Staley, C. A., Cell Growth Differentiation, 8, 269 (1997)], suggesting that Src inhibitors could slow tumor growth. In addition to its role in cell proliferation, Src also acts in stress response pathways, including the hypoxia response. Nude mice studies with colon tumor cells expressing antisense Src message have reduced vascularization [Ellis, L. M., J. Biol. Chem., 273, 1052 (1998)], which suggests that Src inhibitors could be anti-angiogenic as well as anti-proliferative.
Src disrupts E-cadherin associated cell-cell interactions [E. Avezienyte, Nature Cell Bio., 4, 632 (2002)]. A low molecular weight Src inhibitor prevents this disruption thereby reducing cancer cell metastasis [Nam, J. S., Clinical Cancer Res., 8, 2340 (2002)].
Src inhibitors may prevent the secondary injury that results from a VEGF-mediated increase in vascular permeability such as that seen following stroke [Eliceiri, B. P., Mol. Cell., 4, 915 (1999); Paul, R., Nat. Med. 7, 222 (2001)].
Src also plays a role in osteoporosis. Mice genetically engineered to be deficient in Src production were found to exhibit osteopetrosis, the failure to resorb bone [Soriano, P., Cell, 64, 693 (1991); Boyce, B. F., J. Clin., Invest., 90, 1622 (1992)]. This defect was characterized by a lack of osteoclast activity. Since osteoclasts normally express high levels of Src, inhibition of Src kinase activity may be useful in the treatment of osteoporosis [Missbach, M., Bone, 24, 437 (1999)].
Inhibitors of the NMDA (N-methyl-D-asparte) receptor could provide treatment of chronic neuropathic pain [Urban, L. Drug Dev. Res., 54, 159 (2002)]. The activity of NMDA receptors is regulated by Src family kinases (SFKs) (Yu, X. M., Proc. Nat. Acad. Sci., U.S.A., 96, 7697 (1999) and a low molecular weight SFK inhibitor, PP2, decreases phosphorylation of the NMDA receptor NR2 subunit [Guo, W. J. Neuro., 22(14), 6208 (2002)]. SFK inhibitors therefore have potential in the treatment of neuropathic pain.
Tyrosine kinases (TKs) are divided into two classes: the non-transmembrane TKs and transmembrane growth factor receptor TKs (RTKs) [Blume-Jensen, P., Nature, 411, 355 (2001)]. Growth factors, such as epidermal growth factor (EGF), bind to the extracellular domain of their partner RTK on the cell surface which activates the RTK, initiating a signal transduction cascade that controls a wide variety of cellular responses including proliferation and migration. The overexpression of EGF and also of members of the epidermal growth factor receptor (EGFr) family, which includes EGF-r, erbB-2, erbB-3 and erbB-4, is implicated in the development and progression of cancer [Rusch, V., Cytokine Growth Factor Rev., 7, 133 (1996), Davies, D. E., Biochem. Pharmacol., 51, 1101 (1996) and Modjtahedi, E., Int. J. Oncol., 4, 277 (1994)]. Specifically, over expression of the receptor kinase product of the erbB-2 oncogene has been associated with human breast and ovarian cancers [Slamon, D. J., Science, 244, 707 (1989) and Slamon, D. J., Science, 235, 177 (1987)]. Upregulation of EGFr kinase activity has been associated with epidermoid tumors [Reiss, M., Cancer Res., 51, 6254 (1991)]; breast tumors [Macias, A., Anticancer Res., 7, 459 (1987)]; and tumors involving other major organs [Gullick, W. J., Brit. Med. Bull., 47, 87 (1991)].
It is also known that deregulation of EGF receptors is a factor in the growth of epithelial cysts in the disease described as polycystic kidney disease [Du, J., Amer. J. Physiol., 269 (2 Pt 1), 487 (1995); Nauta, J., Pediatric Res., 37(6), 755 (1995); Gattone, V. H., Developmental Biology, 169(2), 504 (1995); Wilson, P. D., Eur. J. Cell Biol., 61(1), 131, (1993)]. The compounds of this invention, which inhibit the catalytic function of the EGF receptors, are consequently useful for the treatment of this disease.
In addition to EGFr, there are several other RTKs including FGFr, the receptor for fibroblast growth factor (FGF); flk-1, also known as KDR, and flt-1, the receptors for vascular endothelial growth factor (VEGF); and PDGFr, the receptor for platelet derived growth factor (PDGF). The formation of new blood vessels, a process known as angiogenesis, is essential for tumor growth. Two natural angiogenesis inhibitors, angiostatin and endostatin, dramatically inhibited the growth of a variety of solid tumors. [O'Reilly, M. S., Cell, 79, 315 (1994); O'Reilly, M. S., Nature Medicine, 2, 689 (1996); O'Reilly, M. S., Cell, 88, 277 (1997)]. Since FGF and VEGF are known to stimulate angiogenesis, inhibition of the kinase activity of their receptors should block the angiogenic effects of these growth factors. In addition, the receptor tyrosine kinases tie-1 and tie-2 also play a key role in angiogenesis [Sato, T. N., Nature, 376, 70 (1995)]. Compounds of the invention that inhibit the kinase activity of FGFr, flk-1, flt-1, tie-1 or tie-2 may inhibit tumor growth by their effect on angiogenesis.
PDGF is a potent growth factor and chemoattractant for smooth muscle cells (SMCs). The renarrowing of coronary arteries following angioplasty is due in part to the enhanced proliferation of SMCs in response to increased levels of PDGF. Therefore, compounds that inhibit the kinase activity of PDGFr may be useful in the treatment of restenosis. In addition, since PDGF and PDGFr are overexpressed in several types of human gliomas, small molecules capable of suppressing PDGFr activity, have potential utility as anticancer therapeutics [Nister, M., J. Biol. Chem. 266, 16755 (1991); Strawn, L. M., J. Biol. Chem. 269, 21215 (1994)].
Other RTKs that could potentially be inhibited by compounds of this invention include colony stimulating factor receptor, the nerve growth factor receptors (trkA, trkB and trkC), the insulin receptor, the insulin-like growth factor receptor, the hepatocyte growth factor receptor and the erythropoietin-producing hepatic cell receptor (EPH).
In addition to the RTKs there is another family of TKs termed the cytoplasmic protein or non-receptor TKs. The cytoplasmic protein TKs have intrinsic kinase activity, are present in the cytoplasm and nucleus, and participate in diverse signaling pathways. There are a large number of non-receptor TKs including Abl, Jak, Fak, Syk, Zap-70 and Csk. Inhibitors of Abl kinase are useful for the treatment of chronic myeloid leukemia as evidenced by STI-571, marketed as Gleevec [Kantarjian, H., N. Engl. J. Med., 346 (9), 645 (2110)].
Two members of the cytoplasmic protein TKs, Lck and ZAP-70 are predominately expressed on T-cells and natural killer (NK) cells. Inhibitors of these kinases can suppress the immune system and therefore have possible therapeutic potential to treat autoimmune diseases such as rheumatoid arthritis, sepsis, and transplant rejection [Kamens, J. S., Current Opin. Investig. Drugs, 2, 1213 (2001); Myers, M., Current Pharm. Design, 3, 473 (1997)]. A low molecular weight Lck inhibitor is effective in preventing allograft rejection [Waegell, W. Transplant. Proceed. 34. 1411 (2002).
Besides TKs, there are additional kinases including those that phosphorylate serine and/or threonine residues on proteins. A major pathway in the cellular signal transduction cascade is the mitogen-activated protein kinase (MAPK) pathway which consists of the MAP kinase kinases (MAPKK), including mek, and their substrates, the MAP kinases (MAPK), including erk [Seger, R., FASEB, 9, 726 (1995)]. When activated by phosphorylation on two serine residues by upstream kinases, such as members of the raf family, mek catalyzes the phosphorylation of threonine and tyrosine residues on erk. The activated erk then phosphorylates and activates both transcription factors in the nucleus and other cellular targets. Over-expression and/or over-activation of mek or erk is associated with various human cancers [Sivaraman, V. S., J. Clin. Invest., 99,1478 (1997)].
As mentioned above, members of the raf family of kinases phosphorylate serine residues on mek. There are three serine/threonine kinase members of the raf family known as a-raf, b-raf and c-raf. While mutations in the raf genes are rare in human cancers, c-raf is activated by the ras oncogene which is mutated in a wide number of human tumors. Therefore inhibition of the kinase activity of c-raf may provide a way to prevent ras mediated tumor growth [Campbell, S. L., Oncogene, 17, 1395 (1998)].
The cyclin-dependent kinases (cdks), including cdc2/cyclin B, cdk2/cyclin A, cdk2/cyclin E and cdk4/cyclin D, and others, are serine/threonine kinases that regulate mammalian cell division. Increased activity or activation of these kinases is associated with the development of human tumors [Garrett, M. D., Current Opin. Genetics Devel., 9, 104 (1999); Webster, K. R., Exp. Opin. Invest. Drugs, 7, 865 (1998)]. Additional serine/threonine kinases include PDK1, SGK and the protein kinases A, B, and C, known as PKA or cyclic AMP-dependent protein kinase, PKB (Akt), and PKC, of which all three play key roles in signal transduction pathways responsible for oncogenesis [Glazer, R. I., Current Pharm. Design, 4(3), 277 (1998)]. Compounds capable of inhibiting the kinase activity of mek, erk, raf, cdc2/cyclin B, cdk2/cyclin A, cdk2/cyclin E, cdk4/cyclin D, PDK1, SGK, PKA, PKB (Akt) or PKC may be useful in the treatment of diseases characterized by abnormal cellular proliferation, such as cancer.
The serine/threonine kinase UL97 is a virion-associated protein kinase which is required for the replication of human cytomegalovirus [Wolf, D. G., Arch. Virology 143(6), 1223 (1998) and He, Z., J. Virology, 71, 405(1997)]. Compounds capable of inhibiting the kinase activity of UL97 may be useful antiviral therapeutics. Since certain bacteria require the action of a histidine kinase for proliferation [Loomis, W. F., J. Cell Sci., 110, 1141 (1997)], compounds capable of inhibiting such histidine kinase activity may be useful antibacterial agents.
Thieno[3,2-b]pyridines, thieno[2,3-b]pyridines and certain pyridine and pyrimidine derivatives have been noted as kinase inhibitors. These compounds differ both in nature and placement of substituents at various positions when compared to the compounds of this invention.